WASHINGTON - Iran is experiencing surprising setbacks in its efforts to enrich uranium, and assessments suggest equipment failures and other difficulties could undermine its effort to ramp up its nuclear program, The Washington Post reported on Thursday.

Former U.S. officials and independent nuclear experts say the technical problems could delay, but probably not stop, Iran's march toward achieving nuclear-weapons capability, the Post reported.

But they said the delays could give the United States and its allies more time to press for a diplomatic solution to Iran's nuclear program, the paper said.

Iran says its nuclear enrichment program is for peaceful energy production, but the United States and other countries suspect Tehran is trying to develop an atomic weapons capability.

The Post story about Iran's diminished capacity to enrich uranium comes amid reports that Tehran plans to begin higher-grade uranium enrichment within days.

The United States has been talking to other major powers about imposing tough new sanctions on Iran because of its nuclear program. The permanent members of the U.N. Security Council plus Germany have been trying to negotiate with Iran over the program, but with little success.

The U.S. Treasury Department on Wednesday imposed sanctions against four firms it says are affiliated with Iran's Revolutionary Guard Corps, as well as the commander of the construction arm of the corps. The action targeted firms involved in Iran's nuclear and missile development.

The Post said U.N. reports over the last year have shown a drop in production at Iran's main uranium enrichment plant, near the city of Natanz.

A new assessment, based on three years of internal data from U.N. nuclear inspections, suggests that Iran's mechanical woes are deeper than previously known, it said.

Through the end of 2009, the Natanz plant appeared to have performed so poorly that sabotage could not be ruled out as an explanation, according to a draft study by David Albright, president of the Institute for Science and International Security, the Post said.

The newspaper said a separate, forthcoming analysis by the Federation of American Scientists also discussed Iran's flagging performance and suggested the failures could increase Iran's appetite for a deal with the West.

Ivan Oelrich, vice president of the federation's Strategic Security Program, told the Post Iranian leaders appeared to have raced into large-scale uranium production for political reasons.

They are really struggling to reproduce what is literally half-century-old European technology and doing a really bad job of it, Oelrich said.

The findings are in line with assessments by numerous former U.S. and European officials and weapons analysts who say that Iran's centrifuges appear to be breaking down at a faster rate than expected, the Post said.

But analysts also warned that Iran remains capable of making enough enriched uranium for a small arsenal of nuclear weapons, if it decides to do so.